The U.S. Navy is revisiting whether its 355-ship plan is sustainable, and whether today's national security environment calls for an even larger naval presence, the Navy's top officer said Friday.

"We're on a path to grow the Navy," said Chief of Naval Operations Adm. John Richardson, adding that the goal is to achieve "the most capable naval force."

Given the current threat environment and the Pentagon's National Defense Strategy, "we're doing a new force-structure assessment, and we'll see where that goes," he told reporters Friday at the Pentagon.

Prior studies by both the Navy and external sources have found that the service's optimal fleet size ranges from the upper 300s to 400s, Richardson said.

But "going forward, we'll take a look at it. I can tell you the security environment has only gotten more sporty, so we'll take that into account," he said. "Technology has started to come into play, and so what counts as a 'naval platform' is going to be an interesting discussion in this … new assessment."

If the 355 number no longer makes sense, "we'll get a new number," Richardson said. "We might hold to it, we may not, [but] the analysis is in progress."

The Navy announced its buildup strategy in late 2016, calling for a fleet of 355 ships by the 2030s.

On Thursday, Todd Harrison, director of the Aerospace Security Project at the Center for Strategic and International Studies and a known Pentagon budget guru, said the plan needs to be more realistic given the uncertainty surrounding future Defense Department budgets, including the fiscal 2020 request.

"Things have to go. The 355-ship Navy is out the window if you want to implement the plan," Harrison said, adding the service will need to review or cancel programs -- carrier, frigate or amphibious ship purchases -- to better align with the NDS while staying pragmatic about costs.

As of January, the service had 287 battle-force ships that were deployable, or capable of conducting operations.

Richardson, who recently came back from visiting ships in the Pacific, Europe and Middle East, said conversations with partners, allies and even rivals such as China need to remain consistent to maintain safety and security.